Methods for the administration of iloperidone

ABSTRACT

The present invention relates to methods for treating a patient with iloperidone or a metabolite thereof, which patient is also being treated with fluoxetine, and lowering risk for QT prolongation.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/060,978, filed Oct. 23, 2013, now abandoned, which is a continuationof U.S. patent application Ser. No. 11/576,178, filed Mar. 28, 2007 (nowU.S. Pat. No. 8,586,610, issued Nov. 19, 2013), which is a 35 U.S.C.§371 national stage entry of International Patent Application No.PCT/US2005/035526, filed Sep. 30, 2005, which claims the benefit of U.S.Provisional Patent Application No. 60/614,798, filed Sep. 30, 2004. Eachof the foregoing patent applications is incorporated herein.

SEQUENCE LISTING

The sequence listing contained in the electronic file titled“VAND-0002-US-CON2SeqID_(—)2014-08-29,” created Aug. 29, 2014,comprising 14 KB, is hereby incorporated herein by reference.

BACKGROUND OF THE INVENTION

Several genes associated with drug metabolism have been found to bepolymorphic. As a result, the abilities of individual patients tometabolize a particular drug may vary greatly. This can proveproblematic or dangerous where an increased concentration of anon-metabolized drug or its metabolites is capable of producing unwantedphysiological effects.

The cytochrome P450 2D6 gene (CYP2D6), located on chromosome 22, encodesthe Phase I drug metabolizing enzyme debrisoquine hydroxylase. A largenumber of drugs are known to be metabolized by debrisoquine hydroxylase,including many common central nervous system and cardiovascular drugs.One such drug is iloperidone(1-[4-[3-[4-(6-fluoro-1,2-benzisoxazol-3-yl)-1-piperidinyl]propoxy]-3-methoxyphenyl]ethanone).Iloperidone and methods for its production and use as an antipsychoticand analgesic are described in U.S. Pat. No. 5,364,866 to Strupczewskiet al. The diseases and disorders that can be treated by administrationof iloperidone include all forms of schizophrenia (i.e., paranoid,catatonic, disorganized, undifferentiated, and residual),schizoaffective disorders, bipolar mania/depression, cardiacarrhythmias, Tourette's Syndrome, brief psychotic disorder, delusionaldisorder, psychotic disorder NOS (not otherwise specified), psychoticdisorder due to a general medical condition, schizophreniform disorder,and substance-induced psychotic disorder. P88 is an active metabolite ofiloperidone. See, e.g., PCT WO2003020707, which is incorporated hereinby reference.

Among the unwanted physiological effects associated with an increasedconcentration of iloperidone or its metabolites is prolongation of theelectrocardiographic QT interval. Mutations in the CYP2D6 gene have beenassociated with a number of drug metabolism-related phenotypes. Theseinclude the ultra rapid metabolizer (UM), extensive metabolizer (EM),intermediate metabolizer (IM), and poor metabolizer (PM) phenotypes.Where a particular drug is capable of producing unwanted physiologicaleffects in its metabolized or non-metabolized forms, it is desirable todetermine whether a patient is a poor metabolizer of the drug prior toits administration.

A number of references are directed toward the identification of CYP2D6mutations and their corresponding phenotypes. For example, United StatesPatent Application Publication No. 2003/0083485 to Milos et al.describes a novel CYP2D6 variant associated with the PM phenotype andmethods for assessing whether an individual possesses the variant priorto the administration of a drug. United States Patent ApplicationPublication No. 2004/0072235 to Dawson describes a primer set useful inidentifying variants of the CYP2D6 gene. Similarly, United States PatentApplication Publication No. 2004/0091909 to Huang describes methods forscreening an individual for variants in the CYP2D6 gene and othercytochrome P450 genes and tailoring the individual's drug therapyaccording to his or her phenotypic profile. Finally, United StatesPatent Application Publication No. 2004/0096874 to Neville et al.describes methods for identifying cytochrome P450 variants.

SUMMARY OF THE INVENTION

The present invention comprises the discovery that treatment of apatient, who has lower CYP2D6 activity than a normal person, with a drugthat is pre-disposed to cause QT prolongation and is metabolized by theCYP2D6 enzyme, can be accomplishing more safely by administering a lowerdose of the drug than would be administered to a person who has normalCYP2D6 enzyme activity. Such drugs include, for example, dolasetron,paroxetine, venlafaxin, and iloperidone. Patients who have lower thannormal CYP2D6 activity are herein referred to as CYP2D6 PoorMetabolizers.

This invention also relates to methods for the identification of geneticpolymorphisms that may be associated with a risk for QT prolongationafter treatment with compounds metabolized by the CYP2D6 enzyme,particularly iloperidone or an active metabolite thereof or apharmaceutically acceptable salt of either (including, e.g., solvates,polymorphs, hydrates, and stereoisomers thereof), and related methods ofadministering these compounds to individuals with such polymorphisms.

The present invention describes an association between geneticpolymorphisms in the CYP2D6 locus, corresponding increases in theconcentrations of iloperidone or its metabolites, and the effect of suchincreases in concentrations on corrected QT (QTc) duration relative tobaseline. Any number of formulas may be employed to calculate the QTc,including, for example, the Fridericia formula (QTcF) and the Bazettformula (QTcB), among others. The present invention includes any suchformula or method for calculating a QTc.

A first aspect of the invention provides a method for treating a patientwith iloperidone or an active metabolite thereof or a pharmaceuticallyacceptable salt of either, comprising the steps of determining thepatient's CYP2D6 genotype and administering to the patient an effectiveamount of iloperidone or an active metabolite thereof or apharmaceutically acceptable salt of either based on the patient's CYP2D6genotype, such that patients who are CYP2D6 poor metabolizers receive alower dose than patients who are CYP2D6 normal metabolizers.

Another aspect of the invention provides a method for treating a patientwho is a CYP2D6 poor metabolizer with iloperidone or an activemetabolite thereof or a pharmaceutically acceptable salt of either,wherein the patient is administered a lower dosage than would be givento an individual who is not a CYP2D6 poor metabolizer.

Another aspect of the invention provides a method of treating a patientwith iloperidone or an active metabolite thereof or a pharmaceuticallyacceptable salt of either comprising the steps of determining whetherthe patient is being administered a CYP2D6 inhibitor and reducing thedosage of drug if the patient is being administered a CYP2D6 inhibitor.

Another aspect of the invention provides a method for determining apatient's CYP2D6 phenotype comprising the steps of administering to thepatient a quantity of iloperidone or an active metabolite thereof or apharmaceutically acceptable salt of either, determining a firstconcentration of at least one of iloperidone and an iloperidonemetabolite in the patient's blood, administering to the patient at leastone CYP2D6 inhibitor, determining a second concentration of at least oneof iloperidone and an iloperidone metabolite in the patient's blood, andcomparing the first and second concentrations.

Another aspect of the invention provides a method for determiningwhether a patient is at risk for prolongation of his or her QTc intervaldue to iloperidone administration comprising the step of: determining apatient's CYP2D6 metabolizer status by either determining the patient'sCYP2D6 genotype or CYP2D6 phenotype. In the case that a patient isdetermined to be at risk for prolongation of his or her QTc interval,the dose of iloperidone administered to the patient may be reduced.

Another aspect of the invention provides a method of administeringiloperidone or an active metabolite thereof, or a pharmaceuticallyacceptable salt of either, for the treatment of a disease or disorder ina human patient comprising the steps of determining the activity of thepatient's CYP2D6 enzyme on at least one of iloperidone and itsmetabolites relative to the activity of a wild type CYP2D6 enzyme andreducing the dose of at least one of iloperidone and itspharmaceutically acceptable salts if the patient's CYP2D6 enzymeactivity is less than that of the wild type CYP2D6.

Another aspect of the invention relates to modifying the dose and/orfrequency of dosing with iloperidone or a pharmaceutically acceptablesalt thereof based on the P88:P95 ratio and/or the (P88+iloperidone):P95ratio in a blood sample of a patient being treated with iloperidone orP88, especially patients susceptible to QT prolongation or to harmfuleffects associated with QT prolongation.

Another aspect of the invention provides a kit for use in determining aCYP2D6 genotype of an individual, comprising a detection device, asampling device, and instructions for use of the kit.

Another aspect of the invention provides a kit for use in determining aCYP2D6 phenotype of an individual, comprising a detection device, acollection device, and instructions for use of the kit.

Another aspect of the invention provides a kit for use in determining atleast one of a P88 to P95 ratio and a P88 and iloperidone to P95 ratioin an individual, comprising a detection device, a collection device,and instructions for use of the kit.

Yet another aspect of the invention provides a method forcommercializing a pharmaceutical composition comprising at least one ofiloperidone, a pharmaceutically acceptable salt of iloperidone, anactive metabolite of iloperidone, and a pharmaceutically acceptable saltof an active metabolite of iloperidone, said method comprising:obtaining regulatory approval of the composition by providing data to aregulatory agency demonstrating that the composition is effective intreating humans when administered in accordance with instructions todetermine whether or not a patient is a CYP2D6 poor metabolizer prior todetermining what dose to administer to the patient; and disseminatinginformation concerning the use of such composition in such manner toprescribers or patients or both.

The foregoing and other features of the invention will be apparent fromthe following more particular description of embodiments of theinvention.

DETAILED DESCRIPTION OF THE INVENTION

Iloperidone is a benzisoxazole-piperidinyl derivative, currently indevelopment for the treatment of CNS disorders. Data fromplacebo-controlled Phase III studies of iloperidone showed a Fridericiacorrection of QT duration (QTcF) increase of 0.1 to 8.5 msec at doses of4-24 mg, when comparing a single ECG at baseline to a single ECG atendpoint. At lower doses of iloperidone (4 mg-16 mg) QTcF prolongationwas minimal (0.1-5 msec). In the most recent study, a greaterprolongation was observed when higher doses of iloperidone (20-24mg/day) were studied. The mean change in the QTcF at doses 20-24 mg/daywas 8.5 msec, and 4.6 msec in the 12-16 mg/day dose range in this study.These data suggest that treatment with iloperidone can be associatedwith prolongation of the QT interval similar to other drugs in thisclass, and that the effect may be dose sensitive in the clinical doserange.

The research leading to the present invention was designed to examinethe effect of different doses of iloperidone relative to the effect ofziprasidone and quetiapine on QTc duration under carefully controlledconditions. To further evaluate the possible relationship betweenexposure to iloperidone and the comparators to QTc duration,reassessment after pharmacological inhibition of the principle metabolicpathways for each drug, under steady-state conditions, was also planned.

Blood samples for pharmacogenetic analysis were collected at screening.Two polymorphisms previously associated with poor metabolizing statuswere genotyped in the CYP2D6 locus and 251 genotypes were collected. Theindividual genotypes were studied for detection of association betweengenotype class and concentrations of iloperidone and its metabolites P88and P95. The functional effect of the polymorphisms was also evaluatedby analyzing the effect of the addition of the CYP2D6 inhibitorparoxetine on the concentrations of the parent drug and its metabolites.

The research leading to the present invention identified a significantassociation between CYP2D6 genotype and concentrations of P88 before theaddition of inhibitors as well as the effect of this association on QTcprolongation.

Iloperidone is a substrate for two P450 enzymes; CYP2D6 and CYP3A4. Mostmetabolic clearance of iloperidone depends on these two enzymes. CYP2D6catalyzes hydroxylation of the pendant acetyl group to form metaboliteP94, which is converted to P95 after some additional reactions. Additionof the CYP2D6 inhibitor fluoxetine, along with iloperidone resulted inincreases of the area under the curve (AUC) for iloperidone and P88 of131% and 119% respectively. Addition of the CYP3A4 inhibitorketoconazole in interaction studies resulted in a 38-58% increase in theconcentrations of iloperidone and its main metabolites P88 and P95. P88has a pharmacological profile including affinity for the HERG channelsimilar to that of iloperidone. P95 is less lipophilic and is dissimilarin its binding profile compared to iloperidone, including having verylow affinity for the HERG channel. For these reasons P95 is regarded asbeing pharmacologically inactive.

The addition of metabolic inhibitors in this study therefore allowed foran evaluation of the effect of increasing blood-concentration ofiloperidone and/or its metabolites on QT duration. More specifically,this study allowed for an evaluation of the effect of iloperidone on QTcbefore and after the addition of the CYP2D6 inhibitor, paroxetine, aswell as before and after the addition of the CYP3A4 inhibitor,ketoconazole.

The CYP2D6 gene is highly polymorphic, with more than 70 allelicvariants described so far. Most embodiments of the present inventionconcern the two most common polymorphisms within the CYP2D6 gene inCaucasian populations, CYP2D6G1846A and CYP2D6P34S (also referred to asCYP2D6C100T). These polymorphisms correspond to nucleotides 3465 and1719, respectively, in GenBank sequence M33388.1 (GI:181303). TheCYP2D6P34S/CYP2D6C100T polymorphism also corresponds to nucleotide 100in GenBank mRNA sequence M20403.1 (GI:181349).

The CYP2D6G1846A polymorphism (known as the CYP2D6*4 alleles,encompassing *4A, *4B, *4C, *4D, *4E, *4F, *4G, *4H, *4J, *4K, and *4L)represents a G to A transition at the junction between intron 3 and exon4, shifting the splice junction by one base pair, resulting inframeshift and premature termination of the protein (Kagimoto 1990,Gough 1990, Hanioka 1990). The CYP2D6P34S/CYP2D6C100T polymorphism(known as the CYP2D6*10 and CYP2D6*14 alleles) represents a C to Tchange that results in the substitution of a Proline at position 34 bySerine (Yokota 1993, Johansson 1994). Both of these polymorphisms havebeen associated with reduced enzymatic activity for different substrates(Johansson 1994, Dahl 1995, Jaanson 2002, see also review by Bertilsson2002)

Methods

A. Samples

128 individuals consented to the pharmacogenetic study. Blood sampleswere collected according to the pharmacogenetics protocol and after theconsent of patients. The DNA was extracted from whole blood by Covanceusing the PUREGENE DNA isolation kit (D-50K).

The 128 individuals that participated were a good representation of thetotal sample of 165 individuals that participated in the trial. 22 of 29total were from the iloperidone 8 mg bid group, 30 of 34 were from theiloperidone 12 mg bid group, 22 of 31 from the 24 mg qd group, 3 of 5 ofthe risperidone group, 28 of 33 of the ziprazidone group, and 23 of 33of the quetiapine group.

B. Genotyping

Genotypes for the CYP2D6G1846A polymorphism were ascertained for 123 ofthe 128 consenting individuals, while genotypes for the CYP2D6C100Tpolymorphism were identified for all 128 participants. Genotyping wasperformed on amplified DNA fragments. The CYP2D6 genomic region wasamplified using a triplex PCR strategy (Neville 2002). In brief, primersused were:

Exons 1 & 2 SEQ. ID. 1 2D6L1F1: CTGGGCTGGGAGCAGCCTC, SEQ. ID. 2 2D6L1R1:CACTCGCTGGCCTGTTT- CATGTC, Exons 3, 4,   SEQ. ID. 3 2D6L2F:CTGGAATCCGGTGTCGAA 5 & 6 GTGG, SEQ. ID. 4 2D6L2R2: CTCGGCCCCTGCACTGTTTC, Exons 7, 8 &  SEQ. ID. 5 2D6L3F: GAGGCAAGAAGGAGTGT 9 CAGGG,SEQ. ID. 6 2D6L3R5B: AGTCCTGTGGTGAGGTGA CGAGG,

Amplification was performed on 40-100 ng of genomic DNA using a GC-richPCR kit (Roche Diagnostics, Mannheim, Germany) according to themanufacturer's recommendations. Thermocycling conditions were asfollows: initial denaturation (3 min 95° C.), 10 cycles of 30 s ofdenaturation (30 s at 95° C.), annealing (30 s at 66° C.), andextension, (60 s at 72° C.) followed by 22 cycles: 30 s at 95° C., 30 sat 66° C., 60 s+5 s/cycle at 72° C. A final extension followed (7 min at72° C.).

Third Wave Technologies, Inc (Madison, Wis.) developed the probe setsfor genotyping. Genotyping was performed on PCR products using theInvader® assay (Lyamichev 1999) (Third Wave Technologies, Inc) accordingto the manufacturer's recommendations.

The genotypes of individuals distributed among the three iloperidonegroups were not significantly different (Table 1A and 1B).

TABLE 1A Genotype frequencies by iloperidone dose class for CYP2D6C100TIloperidone Genotype dose group CC CT TT Total Ilo 8 mg bid  19^(a) 2 122 Ilo 12 mg bid 23 6 1 30 Ilo 24 mg qd 15 6 1 22 Total 57 14 3 74^(a)number of individuals

TABLE 1B Genotype frequencies by iloperidone dose class for CYP2D6G1846AIloperidone Genotype dose group AA AG GG Total Ilo 8 mg bid 0 3 17 20Ilo 12 mg bid 1 6 23 30 Ilo 24 mg qd 1 5 15 21 Total 2 14 55 71C. Statistical Analysis

The genotype effect of the two CYP2D6 polymorphisms on period 1concentrations was evaluated using the following ANOVA model.Concentrations of iloperidone, P88, and P95 at Period 1, withoutinhibitor, at the time at which maximum blood concentration of theparent compound or metabolite was reached (Tmax) were used as thedependent variable, the genotypes of each polymorphism as classes andthe treatment as a covariate. In order to adjust for treatment effectsafter the single dose of iloperidone, the 8 mg bid was coded as 8, the12 mg bid as 12 and the 24 mg qd as 24.

The function of these polymorphisms on the degree of inhibition of theCYP2D6 enzyme was calculated from the ratio of concentrations of P88 andP95 in period 2, after the addition of the inhibitor of CYP2D6. Theconcentrations of iloperidone and/or its metabolites (e.g., P88 and P95)may be determined in period 1 and/or period 2 by any known orlater-developed method or device, including titration.

Results and Discussion

In order to understand the functional significance of the two CYP2D6polymorphisms on the activity of the enzyme, we examined the associationof the various genotypes with the relative concentrations of themetabolites P88 and P95. It is known that P88 is degraded by CYP2D6 andthat CYP2D6 is involved in the synthesis of P95. The relative amounts ofP88 and P95 would therefore be controlled by the activity of the CYP2D6enzyme. We calculated the ratio of P88/P95 before inhibition in Period 1and at the Tmax of the two metabolites, as well as the ratio of P88/P95in Period 2 after the addition of the CYP2D6 inhibitor paroxetine. Inindividuals with the wild type enzyme the concentration of P88 isexpected to increase in Period 2, while in the same period theconcentration of P95 is expected to decline.

For Period 1 the mean P88/P95 ratio among the 91 iloperidone treatedpatients was equal to 1.0 with a range from 0.14 to 8.19. Among the sameindividuals for Period 2 the mean ratio was 2.4 with a range from 0.5 to8.49. The mean ratio of the ratios Period 1/Period 2 was equal to 0.37with a range from 0.11 to 2.75.

Among the genotyped individuals the values were similar with means of 1,2.45 and 0.37 for Period 1, Period 2 and Period 1/Period 2 respectively,indicating no sample bias. For polymorphism CYP2D6G1846A the means weresignificantly different between the three-genotype classes AA, AG andGG. For AA the respective values were 6.1, 3.41, and 1.89, for AG theywere 2.4, 4.2, and 0.52 and for GG 0.57, 1.94 and 0.28 (Table 2).

TABLE 2 Ratios of P88, P95 concentrations according to genotype P88/P95Popula- P88/P95 P88/P95 (Period1/ tion Period1 Period 2 Period2) All 1.0(0.14-8.19) 2.45 (0.50-8.49) 0.37 (0.11-2.75) CYP2D6G1846A AA 6.1(3.96-8.19) 3.41 (2.96-3.87) 1.89 (1.0-2.75) AG 2.4 (0.44-7.0) 4.20(2.2-7.57) 0.52 (0.14-1.28) GG 0.57 (0.14-2.2) 1.94 (0.52-4.71) 0.28(0.11-0.61)

The differences between genotype classes were significant at thep<0.0001 level in ANOVA test. These data suggest that the AA classrepresent a CYP2D6 poor metabolizer as indicated by the high ratio ofP88/P95 in period 1 and the relatively small effect of the addition ofthe inhibitor in Period 2. The AG class seems to exhibit an intermediatephenotype between the poor metabolizer and the wild type with anapproximately 2-fold reduction of the CYP2D6 activity after the additionof the inhibitor, as indicated by the ratio of the ratios (Table 2).This analysis provides a phenotypic characterization of the CYP2D6G1846Apolymorphism as it relates to the metabolism of iloperidone.

Having established a functional role of this polymorphism, we calculatedthe concentrations of P88 at Period 1 at the Tmax of P88 for eachgenotype class. P88 concentrations were significantly (p<0.005) higherfor the AA and AG classes as compared to the GG class for each of thethree iloperidone dose groups (Table 3).

TABLE 3 P88 concentrations in Period 1 according to CYP2D6 genotypeGenotype N obs LSMeans P value AA 2 62.70 <0.0001 AG 14 31.40 GG 5521.03 TRT dose 0.0015 CYP2D6G1846A *TRT dose 0.0058

Although the number of individuals carrying the A allele is limited, theresults obtained in the study consistently suggest that individuals ofthe AA and AG class are expected to experience higher concentrations ofP88 at Tmax as compared with GG individuals. Similar results wereobtained with polymorphism CYP2D6C100T (Table 4 and 5).

TABLE 4 Ratios of P88, P95 concentrations according to genotype P88/P95Popula- P88/P95 P88/P95 (Period1/ tion Period1 Period 2 Period2) All 1.0(0.14-8.19) 2.45 (0.50-8.49) 0.37 (0.11-2.75) CYP2D6C100T CC 0.6(0.14-2.28) 1.93 (0.52-4.71) 0.27 (0.11-0.61) CT 2.2 (0.44-7.0) 4.14(2.2-7.57) 0.49 (0.14-1.28) TT 5.24 (3.56-8.19) 4.19 (2.96-5.74) 1.46(0.62-2.75)

TABLE 5 P88 concentrations in Period 1 according to CYP2D6 genotypeGenotype N obs LSMeans P value CC 57 21.03 CT 14 33.16 <0.0001 TT 351.00 TRT dose <0.0001 CYP2D6C100T*TRT dose 0.0015

This result is expected given the fact that this polymorphism is inalmost complete linkage disequilibrium with the CYP2D6G1846Apolymorphism.

In order to understand whether the difference in concentration of P88 atPeriod 1 Tmax was relevant to the increases in QTc after the addition ofthe inhibitors, we used the observed mean of P88 for the CYP2D6G1846A AGgroup to divide all individuals into two classes. The first includesindividuals with P88 concentrations at Period 3, after the addition ofboth inhibitors, of equal to or less than 34 ng/mL and the second classincludes individuals with P88 concentration greater than 34 ng/mL. Wethen compared the two classes in regards to the QTc change from baselineat Period 3. Using an ANOVA statistic for the first class P88>34 (n=55)the QTc mean change from baseline in Period 3 was 22.7 msec and that forP88≦34 (n=12) the mean QTc for the same period was 7.7 msec. The QTcchanges from baseline for Period 1 and Period 2 according to genotypeand iloperidone dose are given in Table 6 and 7.

TABLE 6 QTc change at Period 1 according to CYP2D6 genotype andiloperidone dose iloperidone Dose Genotype 8 mg bid 12 mg bid 24 mg qdCYP2D6G1846A AA 17.7 (1)^(a) 38.4 (1) AG −0.8 (3) 5.8 (6) 19.0 (5) GG7.8 (17) 11.8 (23) 14.0 (14) CYP2D6C100T TT −8.4 (1) 17.7 (1) 38.4 (1)CT 2.9 (2) 5.8 (6) 19.0 (5) CC 7.8 (17) 11.8 (23) 9.5 (14) ^(a)number ofindividuals

TABLE 7 QTc change at Period 2 according to CYP2D6 genotype andiloperidone dose iloperidone dose Genotype 8 mg bid 12 mg bid 24 mg qdCYP2D6G1846A AA 25.0 (1) 28.4 (1) AG 8.1 (3) 8.7 (6) 20.6 (5) GG 11.7(18) 14.5 (21) 16.4 (15) CYP2D6C100T TT −0.7 (1) 25.0 (1) 28.4 (1) CT12.5 (2) 8.7 (6) 20.6 (5) CC 11.7 (16) 14.5 (21) 16.4 (15)

These results however should be viewed with caution since the number ofobservations is small. If one was, however, to focus on the iloperidone24 mg qd, there is a trend for higher QTc among AA, and AG individualsfor CYP2D6G1846A as compared to GG. This difference disappears after theaddition of the CYP2D6 inhibitor in Period 2.

These observations suggest that the differences in P88 concentrationsduring Period 1 between the different classes of genotypes may berelevant to QTc changes from baseline. Given the small number ofobservations and the unbalanced in regards to genotype design of thestudy, a confirmatory prospectively designed study may be requiredbefore any further interpretation of this data is warranted.Notwithstanding these caveats, the results discussed above show thatpatients can be more safely treated with iloperidone if the dose ofiloperidone is adjusted based on the CYP2D6 genotype of each patient.For example, if a patient has a genotype which results in decreasedactivity of the CYP2D6 protein relative to the wild type CYP2D6, thenthe dose of iloperidone administered to such patient would be reducedto, for example, 75% or less, 50% or less, or 25% or less of the dosetypically administered to a patient having a CYP2D6 genotype thatresults in a CYP2D6 protein that has the same or substantially the sameenzymatic activity on P88 as the wild type CYP2D6 genotype/protein. Forexample, where the normal dosage of iloperidone or otherCYP2D6-metabolized compound administered to an individual is 24 mg perday, an individual with a genotype associated with decreased CYP2D6activity may receive a reduced dosage of 18, 12, or 6 mg per day.

Decreased CYP2D6 activity may be the result of other mutations. Inparticular, it is noted that the CYP2D6*2A mutation includes a CYP2D7gene conversion in intron 1. In some cases, the lower CYP2D6 activity ina CYP2D6 poor metabolizer may be due to factors other than genotype. Forexample, a patient may be undergoing treatment with an agent, e.g., adrug that reduces CYP2D6 activity.

QTc prolongation is correlated to the ratios of P88/P95 and(iloperidone+P88)/P95. The mean ratios among CYP2D6 extensivemetabolizers were 0.57 and 1.00, respectively. As shown above in Tables3 and 5, CYP2D6 poor metabolizers have elevated P88 levels compared toCYP2D6 extensive metabolizers.

As CYP2D6 poor metabolizers comprise approximately 15% of thepopulation, it was found that approximately 15% of those studiedexhibited a P88/P95 ratio greater than 2.0 while the remaining 85%exhibited P88/P95 ratios less than 2.0. Table 8 below shows the leastsquares mean change in QTc for each dosage group. While the results forsome groups are not statistically significant, they do indicate a trendsupporting the hypothesis that QTc prolongation is correlated to P88/P95ratio. Similar results were obtained when cutoff ratios of 3.0 and 4.0were analyzed, providing further support to the hypothesis that theextent of QTc prolongation a patient may experience after treatment canbe predicted by measuring P88 and P95 blood levels.

TABLE 8 Mean QTc Prolongation According to P88/P95 Ratio LSMean LSMeanLSMean LSMean QTc change LSMean QTc change QTc change QTc change fromBaseline QTc change from Baseline P88/P95 from Baseline from Baseline8 + 12 mg from Baseline All Treatment Ratio 8 mg bid 12 mg bid bid 24 qdGroups <2  7.2  8.7  8.3 13.9 10.244 (n = 23) (n = 31) (n = 54) (n = 24)(n = 78) >2 21.3 17.4 18.3 29.4 21.111 (n = 5)  (n = 3)  (n = 8)  (n =5)  (n = 13) P value   0.0725   0.392   0.0815   0.0329  0.0131

Similar results were observed when considering QTc correlation to the(iloperidone+P88)/P95 ratio. Again, as approximately 15% of thepopulation are CYP2D6 poor metabolizers, it was found that approximately15% of those studied exhibited (iloperidone+P88)/P95 ratios greater than3.0 while the remaining 85% exhibited ratios less than 3.0. Table 9below shows the least squares mean change in QTc for each dosage group.While the results for some groups are not statistically significant,they do indicate a trend supporting the hypothesis that QTc prolongationis correlated to (iloperidone+P88)/P95 ratio. Indeed, when cutoff ratiosof 4 and higher were analyzed, similar results were obtained providingfurther support to the hypothesis that the extent of QTc prolongation apatient may experience after treatment can be predicted by measuringiloperidone, P88 and P95 blood levels.

TABLE 9 Mean QTc Prolongation According to (iloperidone + P88)/P95 RatioLSMean LSMean LSMean LSMean QTc change LSMean QTc change QTc change QTcchange from Baseline QTc change from Baseline (ILO + P88)/ from Baselinefrom Baseline 8 + 12 mg from Baseline All Treatment P95 Ratio 8 mg bid12 mg bid bid 24 qd Groups <3  7.2  8.7  8.3 14.4 10.424 (n = 23) (n =31) (n = 54) (n = 24) (n = 78) >3 21.3 15.2 17.3 30.5 20.031 (n = 5) (n= 3) (n = 8) (n = 5) (n = 13) P value   0.0725   0.4223   0.0857  0.0522  0.0278

The starting point for determining the optimum dose of iloperidone is,as discussed above, a dose that has been shown to be acceptably safe andeffective in patients having a CYP2D6 genotype that results in a proteinhaving the same activity on iloperidone and P88 as the wild type CYP2D6protein. Such doses are known in the art and are disclosed, for example,in U.S. Pat. No. 5,364,866 discussed above.

Generally, the dose of iloperidone administered to a patient will bedecreased, as discussed above, if the enzymatic activity of the CYP2D6enzyme on iloperidone and P88 is less than about 75% of that of the wildtype CYP2D6. Enzymatic activity may be determined by any number ofmethods, including, for example, measuring the levels of iloperidoneand/or P88 in an individual's blood. In such a case, the iloperidonedose can be lowered such that measured levels of iloperidone and/or P88are substantially the same as levels measured in the blood ofindividuals having normal CYP2D6 enzymatic activity. For example, if theCYP2D6 enzymatic activity of a patient is estimated by one or moremethods (e.g., genotyping, determination of dextromorphan blood levels)to be 50% of the enzymatic activity normally observed in an individualhaving normal CYP2D6 enzymatic activity, the dose for the patient mayneed to be adjusted to one-half of the dose given to an individualhaving normal CYP2D6 enzymatic activity. Similarly, for ultrarapidmetabolizers, an analogous calculation will lead to the conclusion thata dose adjustment of twice that given an individual having normal CYP2D6enzymatic activity may be needed in order to achieve similar bloodlevels for the parent compound and active metabolites.

Alternatively, the dose of iloperidone administered to a patient may bedecreased based upon the patient's CYP2D6 genotype alone, or upon thepatient's P88:P95 or (iloperidone+P88):P95 ratios. For example, if apatient has a “poor metabolizer” genotype, or has a high P88:P95 or(iloperidone+P88):P95 ratio, the patient's dose of iloperidone may bereduced by, for example, 25%, 50%, or 75%. A patient's genotype can bereadily determined using standard techniques on samples of body fluidsor tissue. Such techniques are disclosed, e.g., in PCT ApplicationPublication Number WO03054226.

While the CYP2D6G1846A (AA or AG) genotype and the CYP2D6C100T (CT orTT) genotype are illustrated herein, the method of the invention canemploy other genotypes that result in decreased activity of the CYP2D6protein on iloperidone and P88. It is within the skill of the art, basedon the disclosure herein, to identify additional CYP2D6 genotypes thatresult in decreased enzymatic activity on iloperidone and P88.

Furthermore, while the disclosure herein focuses on genotype, it isapparent to one of skill in the art that phenotype can also be used asan indicator of decreased activity of the CYP2D6 protein on iloperidoneand P88. For example, McElroy et al. describe a correlation betweenCYP2D6 phenotype and genotyping as determined bydextromethorphan/dextrorphan ratios. Therefore, although it is moreconvenient given the state of the art to look at genotype, if one wereto determine that a given patient expressed a mutant CYP2D6 with loweractivity on iloperidone and P88 than the wild type, or expressedabnormally low amounts of CYP2D6, then that patient would be given alower dose of iloperidone than a patient with wild type CYP2D6, asdiscussed above. Alternative methods for determining the relativeactivity of a patient's CYP2D6 gene include biochemical assays todirectly measure enzymatic activity, protein sequencing to examine theamino acid sequence of a patient's CYP2D6, monitoring transcription andtranslation levels, and sequencing the CYP2D6 gene mRNA transcript. Forexample, Chainuvati et al. describe assessment of the CYP2D6 phenotypeusing a multi-drug phenotyping cocktail (the Cooperstown 5+1 cocktail).

Iloperidone can be formulated into dosage units and administered topatients using techniques known in the art. See, e.g., PCT ApplicationPublication Number WO03054226, US Patent Application Publication Number20030091645, PCT Application Serial Number PCT EP03/07619, and PCTApplication Publication Number WO02064141, all of which are incorporatedherein by reference as though fully set forth.

In addition, the present invention provides a kit for determining apatient's CYP2D6 genotype and/or phenotype. Such a kit may include, forexample, a detection means, a collection device, containers, andinstructions, and may be used in determining a treatment strategy for apatient having one or more diseases or disorders for which iloperidonetreatment is indicated.

Detection means may detect a CYP2D6 polymorphism directly or may detectthe characteristic mRNA of the polymorphic gene or its polypeptideexpression product. In addition, as will be recognized by one of skillin the art, detection means may also detect polymorphisms in linkagedisequilibrium with a CYP2D6 polymorphism. Accordingly, any polymorphismin linkage disequilibrium with the CYP2D6 polymorphisms disclosed inthis application may be used to indirectly detect such a CYP2D6polymorphism, and is within the scope of the present invention.

Detection means suitable for use in the methods and devices of thepresent invention include those known in the art, such aspolynucleotides used in amplification, sequencing, and single nucleotidepolymorphism (SNP) detection techniques, Invader® assays (Third WaveTechnologies, Inc.), Taqman® assays (Applied Biosystems, Inc.), genechip assays (such as those available from Affymetrix, Inc. and RocheDiagnostics), pyrosequencing, fluorescence resonance energy transfer(FRET)-based cleavage assays, fluorescent polarization, denaturing highperformance liquid chromatography (DHPLC), mass spectrometry, andpolynucleotides having fluorescent or radiological tags used inamplification and sequencing.

A preferred embodiment of a kit of the present invention includes anInvader® assay, wherein a specific upstream “invader” oligonucleotideand a partially overlapping downstream probe together form a specificstructure when bound to a complementary DNA sequence. This structure isrecognized and cut at a specific site by the Cleavase enzyme, releasingthe 5′ flap of the probe oligonucleotide. This fragment then serves asthe “invader” oligonucleotide with respect to synthetic secondarytargets and secondary fluorescently-labeled signal probes contained in areaction mixture. This results in the specific cleavage of the secondarysignal probes by the Cleavase enzyme. Fluorescence signal is generatedwhen this secondary probe, labeled with dye molecules capable offluorescence resonance energy transfer, is cleaved. Cleavases havestringent requirements relative to the structure formed by theoverlapping DNA sequences or flaps and can, therefore, be used tospecifically detect single base pair mismatches immediately upstream ofthe cleavage site on the downstream DNA strand. See, e.g., Ryan et al.,Molecular Diagnosis, 4; 2:135-144 (1999); Lyamichev et al., NatureBiotechnology, 17:292-296 (1999); and U.S. Pat. Nos. 5,846,717 and6,001,567, both to Brow et al., all of which are hereby incorporatedherein by reference.

Another preferred embodiment of a kit of the present invention includesa detection means comprising at least one CYP2D6 genotypingoligonucleotide specific to alleles known to predict a patient'smetabolizer phenotype. More particularly, the means comprises anoligonucleotide specific for the CYP2D6G1846A or CYP2D6C100Tpolymorphism. The means may similarly comprise oligonucleotides specificfor each polymorphism as well as the wild type sequence.

Detection methods, means, and kits suitable for use in the presentinvention are described in International Publication Nos. WO 03/0544266and WO 03/038123, each of which is hereby incorporated herein byreference. It should also be understood that the methods of the presentinvention described herein generally may further comprise the use of akit according to the present invention.

Collection devices suitable for use in the present invention includedevices known in the art for collecting and/or storing a biologicalsample of an individual from which nucleic acids and/or polypeptides canbe isolated. Such biological samples include, for example, whole blood,semen, saliva, tears, urine, fecal material, sweat, buccal smears, skin,hair, and biopsy samples of organs and muscle. Accordingly, suitablecollection devices include, for example, specimen cups, swabs, glassslides, test tubes, lancets, and Vacutainer® tubes and kits.

The present invention encompasses treatment of a patient for any diseaseor condition that is ameliorated by administration of iloperidone. Asdiscussed above, such diseases or conditions include, for example,schizoaffective disorders including schizophrenia, depression includingbipolar depression, as well as other conditions such as cardiacarrythmias, Tourette's syndrome, psychotic disorders and delusionaldisorders.

A related aspect of the invention is a method for obtaining regulatoryapproval for a pharmaceutical composition comprising iloperidone or anactive metabolite thereof, or a pharmaceutically acceptable salt ofeither, which comprises including in proposed prescribing informationinstructions to determine whether or not a patient is a CYP2D6 poormetabolizer prior to determining what dose to administer to the patient.In another related aspect, the invention is a method for commercializing(i.e., selling and promoting) pharmaceutical compositions comprisingsuch compounds said method comprising obtaining regulatory approval ofthe composition by providing data to a regulatory agency demonstratingthat the composition is effective in treating humans when administeredin accordance with instructions to determine whether or not a patient isa CYP2D6 poor metabolizer prior to determining what dose to administerto the patient and then disseminating information concerning the use ofsuch composition in such manner to prescribers (e.g., physicians) orpatients or both.

Another aspect of the invention is a method for obtaining regulatoryapproval for the administration of iloperidone based, in part, onlabeling that instructs the administration of a lower dose if thepatient is already being administered a CYP2D6 inhibitor, e.g.,paroxetine, etc.

While this invention has been described in conjunction with the specificembodiments outlined above, it is evident that many alternatives,modifications and variations will be apparent to those skilled in theart. Accordingly, the embodiments of the invention as set forth aboveare intended to be illustrative, not limiting. Various changes may bemade without departing from the spirit and scope of the invention asdefined in the following claims.

What is claimed is:
 1. A method of decreasing a risk of QT prolongationin a patient being treated for schizophrenia with iloperidone, themethod comprising: administering to the patient a dose of iloperidonethat is 24 mg/day if, and because, the patient is not being treated withfluoxetine; and administering to the patient a dose of iloperidone thatis 12 mg/day if, and because, the patient is being treated withfluoxetine.